Method of fabricating a micro-technical structure, and micro-technical component

ABSTRACT

The invention relates to a method for fabricating in particular a TMR element for use in a MRAM, wherein a mask is arranged on a substrate and structured in such a manner that it shadows but does not cover a surface region of the substrate, and wherein material of the structure which is to be fabricated is then deposited on the substrate in a directed deposition process. The invention also relates to a component with a micro-technical structure which has been fabricated in this manner.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The invention relates to a method for fabricating a micro-technicalstructure, in particular a ferromagnetic structure for use in a MRAM(Magneto-resistive Random Access Memory), wherein a mask is structured,the mask is arranged on a substrate and the micro-technical structure isgenerated on a surface region of the substrate which is not covered bythe mask. The invention also relates to a micro-technical componenthaving a substrate and a micro-technical structure arranged on thesubstrate.

Particularly in the case of microelectronic components, i.e. electroniccomponents whose structure dimensions reach the micron range and eventhe sub-micron range, special, highly developed structuring processesare employed. Structures with particularly small dimensions are desiredin particular for the development of data memories. However, structuringprocesses of this type are also employed for microstructures for otherapplications, such as for example write and/or read heads for harddisks.

It is known to use lithography processes and etching processes tostructure thin layers and layer systems. In particular, in this case thelithography processes generate structures in photo resist layers, andetching processes transfer these structures into the thin layers orlayer systems which lie below the photo resist layers. Anisotropicplasma etching processes, such as for example RIE (Reactive IonEtching), RSE (Reactive Sputter Etching), ECR etching (ElectronCyclotron Resonance etching), ICP etching (Inductively Coupled Plasmaetching) and CAIBE (Chemically Assisted Ion Beam Etching) are known forlayer structuring in the micron (μm) and sub-micron (sub-μ) range. Withetching processes of this type, it is necessary for the reactionproducts formed from the material which is to be etched away to passinto the gas phase so that they can be removed from the reactionchamber. Numerous materials which are suitable for microstructures interms of their physical properties cannot be satisfactorily structuredusing some or all of the known etching processes, since the reactionproducts which are formed during the etching form a passivating layer onthe surface of the material which is to be etched, thus preventingfurther etching and removal of the material. Furthermore, etchingprocesses in general may lead to redeposition of the material which hasbeen etched off, for example on etching masks, the edges of the regionswhich are to be etched and on parts of the etching chamber. This leads,for example, to undesirable inclined etching flanks and changes to thedimensions of etching masks. However, electrical short circuits causedby electrically conductive redeposition on the flanks of multilayersystems may also occur.

Particularly for use in future MRAMs (Magneto resistive Random AccessMemories), structures with ferromagnetic materials, such as Ni, Fe andCo, as well as alloys comprising these materials, are produced andtested for suitability. When structuring these materials using etchingprocesses, the nonvolatile passivating layers described above areformed. S. J. Pearton, et al., in the publication “High Rate Etching ofMetals for Magneto Electronic Applications,” Electrochemical SocietyProceedings Vol. 97-21, pages 270-85 (hereinafter “Pearton”) proposeusing a plasma etching process with a high ion density, in order toavoid the formation of a disruptive passivating layer. According toPearton, the high ion density leads to a high ion flux, so that normallynonvolatile reaction products are sputtered away. Pearton proposesetching ferromagnetic metal alloys, such as NiFe and NiFeCo, in thepresence of Cl in the etching gas. Although this leads to higher etchingrates than with pure Ar etching gas, chlorine-containing compounds thatare thereby formed lead to corrosion of the metal alloys after theetching. The chlorine-containing compounds have to be removed in afurther process step.

It is reported in the publication “Assessment of Dry Etching Damage inPermalloy Thin Films” by S. D. Kim et al., Journal of Applied Physics,Vol. 85, No. 8, pages 5992-5994, dated Apr. 15, 1999, that plasma dryetching processes, such as IBE (Ion Beam Etching) and RIE (Reactive IonEtching), in the case of NiFe (Permalloy), lead to the magneticproperties being impaired, on account of the bombardment with ions.

A further drawback of plasma etching techniques is the low selectivityof the etching action both with respect to the etching mask and withrespect to the substrate on which the material to be etched is arranged.This leads to etching masks being worn away and to undesirablestructuring of the substrate.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a method offabricating a micro-technical structure and a micro-technical componentwith a micro-technical structure formed on a substrate, which overcomesthe above-mentioned disadvantages of the heretofore-known devices andmethods of this general type and wherein the generation of the finallateral dimensions of the structure (structuring) effects and/or causesand/or has caused as far as possible no damage to the structure and thesubstrate. Particularly in the case of structures comprisingferromagnetic materials, the magnetic properties of these materials arenot to be adversely affected by the structuring and subsequent processsteps caused by the structuring.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a method of fabricating a micro-technicalstructure, in particular a ferromagnetic structure for an MRAM. Themethod comprises the following steps:

providing a substrate;

forming a structured shadow mask on the surface of the substrate, anddefining on the surface an uncovered surface region not covered by themask and a shadow region shadowed but not covered by the mask; and

depositing material through the mask in a directed deposition processand forming the micro-technical structure on the uncovered surfaceregion of the substrate not covered by the mask.

With the above and other objects in view there is also provided amicro-technical component, comprising:

a substrate; and

a micro-technical structure formed on the substrate and extending alonga common interface with the substrate, the micro-technical structurehaving been fabricated with the above-outlined method, and a shaping ofa surface or at least one layer of the structure at an edge of thestructure resulting only from a deposition of the structure material inthe directed deposition process.

An important idea of the present invention is to arrange the material ofthe structure on the substrate in the same process step as at least partof the structuring of the structure which is to be fabricated. Thestructure is laterally delimited in at least one location of thesubstrate purely by the fact that the structure material is arranged onthe substrate. This eliminates the need for a following etching process,which could cause damage to the structure and/or the substrate.

In one embodiment, a mask is structured and arranged on the substrate insuch a manner that the mask shadows but does not cover a surface regionof the substrate. In the direction of a surface normal, the mask issituated at a distance from the surface in this surface region. Then,material of the structure which is to be fabricated is deposited on thesubstrate in a directed deposition process. The term “directeddeposition process” is understood as meaning a deposition processwherein the material which is to be deposited generally moves in adirected manner, namely in a straight line, toward the depositionlocation. This does not rule out the possibility of the direction ofmovement of the material which is to be deposited being changed, forexample by the interaction of a plurality of particles of the materialbeing deposited and/or deflection from structure edges and/or byscattering on fixed structures. However, most of the material which isto be deposited will move substantially in a straight line from adeposition source or a source region of the deposition to the depositionlocation.

A significant advantage of this embodiment consists in the fact thatsignificantly less material is deposited on the shadowed surface regionof the substrate than on uncovered and unshadowed surface regions of thesubstrate. Furthermore, even within the shadowed region the depositionrate is dependent on the distance between the deposition location andthe edge of the shadowed region. Generally, the deposition rate willfall continuously at increasing distance from the edge of the shadowedregion. The dimensioning of the mask and setting of the distance betweenthe mask and the shadowed surface region of the substrate, as well asthe nature and process management of the directed deposition process,therefore allows the local distribution of the thickness of thedeposited material in the shadowed region to be controlled. It istherefore possible, for example, to produce a more or less steep flankof the deposited material at the edge of the shadowed region.

In a special embodiment of the invention, wherein, by deposition of aplurality of layers on top of one another on the substrate, the in thiscase multilayer micro-technical structure is generated, the controloptions referred to above can be utilized to good effect. For example,it is possible for a layer which is deposited at a later stage tocompletely cover a layer which was deposited at an earlier stage all theway over the edge of the layer which was deposited earlier. The layerdeposited later is, for example, a tunnel barrier, a diffusion barrierand/or a separating layer which prevents the material of the layerdeposited earlier from coming into contact with material of a layerwhich was deposited even later than the separating layer. In particular,a TMR (Tunnel Magneto resistance) element or a GMR (Giant Magnetoresistance) element can be produced in this way. TMR and GMR elementscan be used, for example, as memory elements for future MRAMs.

In particular, the layer which was applied later and the layer which wasapplied earlier are produced, in deposition processes, with a differentangular distribution of the material which is to be deposited. In thiscontext, the term angular distribution is understood as meaning theangular distribution of the material to be deposited from the viewpointof a source of the deposition process or a source region of thedeposition source. Sources of the deposition process may, for example,be a sputtering target, an electrically heatable evaporation sourceand/or the target of an electron beam evaporator. The angulardistribution can be set in particular by ionization of the material tobe deposited and by means of electrical fields. Pure PVD (Physical VaporDeposition) processes have a more uniform angular distribution than PVDprocesses with ionized deposition material in the presence of electricfield forces. In the case of electron processes, the flux of depositionparticles in the direction of the electric field forces is greater.

The mask which shadows the surface region of the substrate may bestructured before, during and/or after its application to the substrate.It is advantageously arranged and structured in such a manner that afirst part of the mask covers a surface region of the substrate and asecond part of the mask forms an overhang which is supported against thesubstrate by the first part and which defines the shadowed surfaceregion. The length of the overhang is preferably adapted to theabovementioned factors of influence for controlling the deposition ofthe structure material in such a manner that the edge of the structuregenerated does not abut the mask. In this case, in a following methodstep, filler material may be arranged between the mask and the edge,serving, for example, as electrical insulation or a diffusion barrier.

In accordance with a particularly preferred feature of the invention,when arranging the mask on the substrate initially a first mask layer isdeposited on the substrate. Then, a second mask layer is deposited onthe first mask layer. Therefore, in the region wherein themicro-technical structure is subsequently to be generated, the substrateis covered by two mask layers which lie on top of one another. Tostructure the mask, the second mask layer and the first mask layer areremoved again in defined regions. The result is a surface region of thesubstrate which is neither covered nor shadowed and is thereforeavailable for the deposition of the structure material. The first andsecond mask layers preferably comprise different materials. The processfor removal of the first and second mask layers may be a single-stage ormultistage process. Then, in an isotropic etching process, additionalmaterial of the first mask layer is removed between the second masklayer and the substrate. This results in the overhang which is formed bythe second mask layer.

Often, there is a need for micro-technical structures which are intendedto have a continuous encircling edge with a defined local arrangement.By way of example, microelectronic structures at a defined location aredeposited directly on a material which is used for electrical connectionto the microelectronic structure. If the structure is not arranged atprecisely the correct position, the electrical contact is insufficientand short circuits may occur at a later stage. The above-describedarrangement and structuring of the mask offers a reliable solution tothis problem. The first and second mask layers can be opened up atprecisely the correct location, for example by lithographic methods. Theedges of the regions which have been opened up in this way substantiallyalso define the edges of the structure which is subsequently to befabricated. In particular, the shadowed surface region forms acontinuous encircling edge around an unshadowed surface region of thesubstrate, which is to be provided with the micro-technical structure.

In order, for example, to electrically insulate the micro-technicalstructure and/or mechanically stabilize the structure, the shadowedsurface region of the substrate and/or the surface of themicro-technical structure is preferably covered with a filler materialafter the micro-technical structure has been generated. Particularlywith the above-described type of arrangement and structuring of themask, it is possible for the entire region which has been opened up inthe first and second mask layers to be filled with the filler material.A planar surface is then formed by removing part of the mask and part ofthe filler material. The planar surface then, for example, allows thedeposition of further planar layers and therefore allows the generationof further structure elements in a manner known per se.

The micro-technical component according to the invention is wherein thestructure, which extends along the common interface with the substrate,has been fabricated using the method according to the invention, and theshaping of the structure surface or of at least one layer of thestructure at the edge of the structure is exclusively the result of thedeposition of the structure material in the directed deposition process.Therefore, the surface of the edge of the structure or of the layer hasno traces whatsoever of a subsequent structuring measure carried outafter the end of the deposition of the structure material. Inparticular, it has no residues of chemicals and/or ions which are usedin an etching process, and, as is typical for a deposition process, thesurface profile is slightly irregular, i.e. the surface has the typicalroughness. This can be established by X-ray structural analysis tests ina corresponding way to that described in the abovementioned publicationby S. D. Kim et al.

Particularly if the micro-technical structure has been fabricated with asufficiently long overhang of the shadow mask, the structure at its edgehas a characteristic S-shaped surface. In this area, the thickness ofthe structure increases in an S-shape from approximately 0 to a meanvalue for the structure.

The structure is preferably enclosed by an adjoining filler materialwhich is applied to the substrate.

A significant advantage of the invention is that there is no need forcomplex plasma etching processes to structure the micro-technicalstructure. To structure the shadow mask it is possible, for example, touse much simpler etching installations with proven etching processeswhich are used for damascene processes. Particularly in the case ofmicroelectronic structures, these installations are already in use forfabrication of the electrical connection lines. On account of thein-situ structuring of the structure by targeted, locally restricteddeposition of the structure material, damage to the structure and/or thesubstrate caused by structuring etching processes is avoided.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a method for fabricating a micro-technical structure, andmicro-technical component, it is nevertheless not intended to be limitedto the details shown, since various modifications and structural changesmay be made therein without departing from the spirit of the inventionand within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-7 are diagrammatic side views illustrating various stages in thefabrication of a micro-technical structure;

FIG. 8 is a section through an exemplary construction of amicro-technical structure;

FIG. 9 is a section through an exemplary construction of amicro-technical structure;

FIG. 10 is a diagram showing simulation results representing across-sectional profile of a micro-technical structure at its edge; and

FIGS. 11A-11C are diagrammatic sections showing various stages of theintegration of a TMR element in an MRAM memory component.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is shown a cross section througha substrate S with layers arranged thereon. For the sake of simplicity,in the text which follows the terms “top” and “bottom” refer to theillustration which has been selected in FIGS. 1 to 11, without thisbeing intended to restrict the implementation of the invention. Thesubstrate S may, for example, be a CMOS, bipolar, BiCMOS or GaAssemiconductor circuit, including metallization structures. A firstdielectric layer D1 comprising a first dielectric material is depositedon the substrate S. A second dielectric layer D2 made from a seconddielectric material, which is different from the first dielectricmaterial, is then deposited on the layer D1. A lithographically producedmask LM is in turn arranged on the layer D2. The mask LM has a hole-likeaperture O which passes all the way through the mask layer.

Starting from the structure illustrated in FIG. 1, in a followingprocess step the opening O is transferred, with dimensions which are asclosely accurate as possible, into the layer D2 using an anisotropicetching process, i.e. a continuous opening with, as far as possible, thesame opening which is produced in layer D2. Then, in an isotropicetching process, the material of the layer D1 is etched, so that anopening with a greater width than the width of the opening in the layerD2 is formed in the layer D1. The isotropic etching process is aselective etching process wherein the material of the layer D2 and thatof the substrate S are etched at most slightly. Then, the mask LM isremoved. The resulting structure is illustrated in FIG. 2.

The layers D1, D2 which have been structured in this way form a shadowmask SM, the material of the layer D2, at the opening, forming acontinuous, encircling overhang U; the length of the overhang U is equalto the difference between the radii of the circular openings in thelayers D1, D2. Alternatively, the openings may also be rectangular or ofsome other shape.

By directed deposition, e.g. by sputtering of the material to bedeposited or by direct vaporization of the material to be deposited, astructure element SE is deposited on the surface of the substrate S(FIG. 3). Because part of the surface of the substrate S is shadowed bythe overhang U, and because of the directionality of the depositionprocess, a flank or an edge R of the structure element SE is formed atthe edge of the shadowed surface region. Since material is alsodeposited on the layer D2 during the deposition process, therebyreducing the width of the opening in layer D2, and since the layerthickness of the structure element SE increases continuously, the edge Rdoes not run perpendicular to the surface of the substrate S. Unlikewith known structuring processes using etching techniques, whereinflanks of this type are generally undesirable, since, for example, theymake it more difficult to laterally electrically insulate the structure,the shape of the edge R is not in this case a drawback. If insulation isactually required, sufficient space remains between the edge R and thematerial of the layer D1 to achieve good insulation. Furthermore, aswill be explained in more detail, the inclined profile of the edge R maybe an advantage if a further, thin layer is to be deposited on thestructure element SE.

As shown in FIG. 10, the edge R, in cross section, is not rectilinear.FIG. 10 shows the result of a simulation of the deposition of astructure element which is composed of three layers. FIG. 10 illustratespart of the opening shown in FIG. in layers D1, D2. The measurement unitof the values plotted on the horizontal and vertical axes is, forexample, μm (micron). The lower and upper layers of the structureelements consist of Ta and the interlayer consists of Al. FIG. 10clearly shows the typical S-shaped cross-sectional profile of the edgeR. Starting from a mean thickness for the thickness of the structureelement, as is present, for example, at value 0.1 on the horizontalaxis, the thickness initially decreases progressively, i.e. more quicklythan in linear fashion, toward the edge, and then, after a reversalpoint has been reached, decreases digressively, i.e. more slowly than inlinear fashion, toward the edge. The deposition AB (FIG. 3 and FIG. 10)leads to a reduction in the width of the opening in the layer D2 andtherefore influences the shaping of the edge R. It can clearly be seenfrom FIG. 10 that the upper layer made from Ta scarcely has any materialleft at the far end of the edge R, on account of the closing gap betweenthe structure element and the layer D2.

After the structure element SE has been fabricated, the opening in thelayers D1, D2 is completely filled up with a filler material, so that afiller layer FS is formed. This takes place, for example, by means of aCVD (Chemical Vapor Deposition) process, wherein Sio2 or Si3N4 isdeposited as filler material. Further options are to deposit spin-onglass or polyimide or to use other known filling processes. It is notnecessary for the opening in the layers D1, D2 to be filled up withoutany voids. Preferably, however, the structure element SE is completelycovered by the filler material. Preferably, after the structureillustrated in FIG. 4 has been achieved, the material of the fillerlayer FS and of the shadow mask SM is removed until regions whereincavities could be present have been completely removed from the overallstructure. This is done, for example, by CMP (Chemical MechanicalPolishing), until the material of the layer D2 has been completelyremoved (FIG. 5). Etching processes, such as plasma etching andwet-chemical etching, may also be used. The fact that the structureelement SE is completely covered protects it from damage during thisprocess and any further process steps. If, after partial removal of thefiller material and of the material of the shadow mask SM, the openingin the shadow mask SM or in the layers D1, D2 is not yet sufficientlyfilled, this filling step can then be repeated under simplifiedconditions. The filling operation is made easier since the aspect ratioof the opening (ratio of the opening depth to the opening width) isconsiderably reduced. Advantageously, the material of the layer D2 andthe filling layer FS down to below the level of the lower edge of thelayer D2 is removed first, before renewed application of filler materialis commenced.

Particularly if the structure element SE is to be exposed on itssurface, for example in order to make electrical contact therewith,further material of the shadow mask SM (the layer D1) and of the fillerlayer FS can be removed by CMP, until the surface of the structureelement SE is exposed (FIG. 6). Alternatively, the surface of thestructure element SE is exposed by means of a lithographic process andsubsequent etching of a hole. The etching takes place, for example, byRIE (Reactive Ion Etching). The resulting structure is illustrated inFIG. 7.

FIG. 8 and FIG. 9 show different variants of the form of a structureelement SE, as has been fabricated, for example, in the process stepsshown in FIG. 1 to FIG. 7.

The structure element SE illustrated in FIG. 8 has a base layer GS witha substantially planar surface and a covering layer DS, likewise with asubstantially planar surface. In this exemplary embodiment, the coveringlayer DS does not cover or does not completely cover the edge of thebase layer GS. This structure can easily be achieved through the factthat the covering layer DS and the base layer GS can be applied indeposition processes with increasing directionality, or withincreasingly marked nonuniform angular distribution. In this way, thematerial of the covering layer DS no longer reaches the edge region ofthe base layer GS.

The form of the structure element SE shown in FIG. 9 differs from thatshown in FIG. 8 in that an additional interlayer ZS has been appliedbetween the base layer GS and the covering layer DS. The interlayer ZSwas applied in a deposition process with lower directionality or moreuniform angular distribution, so that the edges of the base layer GS arecompletely covered by the material of the interlayer ZS. In this way itis possible, for example, to fabricate TMR or GMR elements for use inMRAM components. In TMR elements, the base layer (for example the hardmagnetic layer) consists, for example of NiFeCo, the interlayerconsists, for example, of Al₂O₃, and the covering layer DS consists, forexample, of NiFe (for example the soft magnetic layer).

The manufacturing processes which have been described with reference toFIG. 1 to FIG. 7 are carried out, for example, as follows: the coveringlayer D1 is fabricated with a layer thickness of 50 nm using a PECVD(Plasma Enhanced Chemical Vapor Deposition) process. The material is,for example, Si₃N₄. The layer D2 consists, for example, of SiO₂, whichhas been applied with a layer thickness of 200 nm, likewise using aPECVD process. During the photolithography for generating the mask LM,holes with a width of approx. 350 nm were structured. The structuring ofthe layer D2 took place using an anisotropic RIE (Reactive Ion Etching)process with CHF₃, CF₄ and Ar etching gas. The isotropic etching of thelayer D1 was effected by RIE, plasma etching and/or by CDE (Chemical DryEtching). Suitable etching gases are CF₄ with O₂, SF₆ and NF₃.Alternatively, the hole may be made in the layer D1 by wet-chemicalmeans in the presence of H₃PO₄ and at temperatures of 160 to 180° C.

The structure element SE is, for example, a TMR element which has beenfabricated in the form explained with reference to FIG. 9 by adaptingthe directionality of the deposition process. The pressure and the basicnature of the deposition process were adapted accordingly. In asputtering process, the target-substrate distance and the electricalvoltage of the high frequency of a sputtering installation were changed.As has already been described, the degree of ionization of the gas inthe process chamber is available as a further parameter (IMP process, asdistinct from the standard PVD process). During the removal of the layerD1 outside the cell array ZF (FIG. 11a), an RIE process in the presenceof CF4 with Ar or SF₆ with He was used. The lithography step requiredfor this purpose is not critical with regard to resolution and overlayadjustment accuracy. The layer D3 (FIG. 11) was deposited using a PECVDprocess with a layer thickness of 50 nm from the material Si₃N₄. Thelayer D4 was likewise deposited in a PECVD process with a layerthickness of 400-600 nm as SiO₂. The structuring of the upper conductortracks Lo (FIG. 11) in the cell array ZF and for the vias in theperiphery P was achieved using a damascene process, i.e. byphotolithography, RIE of the SiO₂ layer D4 selectively with respect tothe layer D3 in the presence of CHF₃ and CF₄ and Ar, by RIE of the layerD3 selectively with respect to the uppermost layer material of thestructure element and selectively with respect to the material of thefiller layer FS in the presence of CF4 and Ar, by deposition of a TaN/Tadouble layer with a total thickness of 15 nm as diffusion barrier DB ina sputtering process, and by deposition of Cu with a thickness of atleast 200 nm by sputtering. Finally, the planar surface illustrated inFIG. 11C was achieved using a CMP process, by removing the Cu and theTaN or Ta selectively with respect to the SiO2 of the layer D4.

FIGS. 11A to 11C show cross sections through part of a cell array ZFwith adjoining periphery region. By way of example, only one TMR cell ofthe cell array ZF is illustrated, namely the structure element SE whichhas been fabricated, for example, using a method as has been describedwith reference to FIG. 1 to FIG. 9. The cell array ZF is a field ofmemory cells, as in the structure element SE for a MRAM.

After the construction illustrated in FIG. 9 has been reached, firstlythe layer D1 is removed in the region of the periphery P. Then, a thirddielectric layer D3 is applied to the planar surface (in the cell arrayZF) formed by the layer D1, the filler layer FS and the structureelement SE or to the already existing lower conductor track L_(u) formaking electrical contact with the cell array or a part of the cellarray. The lower conductor track L_(u) is already embedded in adiffusion barrier DB which, in turn, is delimited at the bottom by theactual substrate S of the construction. Around the lower conductor trackL_(u), the diffusion barrier DB is laterally delimited by a dielectricmaterial. Furthermore, the lower conductor track L_(u) may also bedelimited on its upper side by a diffusion barrier (not shown), which inthis case is situated between the lower conductor track L_(u) and thestructure element SE. A fourth dielectric layer D4 is then applied tothe third dielectric layer D3. The result is the overall constructionshown in FIG. 11A.

Then, upper conductor tracks L_(o) (in the cell array ZF) or vias V (inthe periphery P) are fabricated using the damascene technique (inlaytechnique). For this purpose, first of all holes or trenches areproduced through the layers D3, D4 to the structure elements SE or tothe lower conductor track L_(u) using a lithography process withsubsequent etching (FIG. 11B). Then, firstly a diffusion barrier DB isintroduced into the holes which have been generated, so that itcompletely covers the edge of the holes. The diffusion barrier DB isused in particular to prevent diffusion of the material of the conductortracks L_(o), V (for example Cu) which is yet to be introduced. Then,the elongate contact holes are filled with electrically conductivematerial. The final step is the planarization of the surface. This stateis illustrated in FIG. 11C.

We claim:
 1. A method of fabricating a micro-technical structure, whichcomprises the following steps: providing a substrate with a surface;forming a structured shadow mask on the surface of the substrate, anddefining on the surface an uncovered surface region not covered by themask and a shadow region shadowed but not covered by the mask; anddepositing material through the mask in a directed deposition processand forming the micro-technical structure on the uncovered surfaceregion of the substrate not covered by the mask.
 2. The method accordingto claim 1, which comprises depositing materials to form a ferromagneticstructure for an MRAM.
 3. The method according to claim 1, wherein theforming step comprises arranging and structuring the mask such that afirst part of the mask covers a surface region of the substrate and asecond part of the mask forms an overhang which is supported against thesubstrate by the first part and which defines the shadow region.
 4. Themethod according to claim 3, wherein the forming step comprisesinitially depositing a first mask layer on the substrate and depositinga second mask layer on the first mask layer, and structuring the mask byremoving the second mask layer and the first mask layer in definedregions and isotropically etching to remove additional material of thefirst mask layer between the second mask layer and the substrate.
 5. Themethod according to claim 1, wherein the shadow region forms acontinuous encircling margin around the uncovered surface region notshadowed by the mask on which the micro-technical structure is produced.6. The method according to claim 1, which further comprises, after thestep of forming the micro-technical structure, covering at least one ofthe shadow region of the substrate and a surface of the micro-technicalstructure with a filler material.
 7. The method according to claim 6,which comprises forming a planar surface by removing part of the maskand part of the filler material.
 8. The method according to claim 1,wherein the depositing step comprises forming the micro-technicalstructure by depositing a plurality of layers one above the other on thesubstrate.
 9. The method according to claim 8, which comprises forming alayer on a previously applied layer of the structure, and fabricatingthe layers in deposition processes with different angular distributionsof the material being deposited.